Bul. 140U
Q and M-Frame Circuit Breaker
Instruction Leaflet for Installation and Operation for
Thermal Magnetic Trip Units
General Information
WARNING
DO NOT ATTEMPT TO INSTALL OR PERFORM
MAINTENANCE ON EQUIPMENT WHILE ITS IS
ENERGIZED. DEATH, SEVERE PERSONAL INJURY,
OR SUBSTANTIAL PROPERTY DAMAGE CAN
RESULT FROM CONTACT WITH ENERGIZED
EQUIPMENT. ALWAYS VERIFY THAT NO VOLTAGE IS
PRESENT BEFORE PROCEEDING WITH THE TASK,
AND ALWAYS FOLLOW GENERALLY ACCEPTED
SAFETY PROCEDURES.
ALLEN-BRADLEY IS NOT LIABLE FOR THE
MISAPPLICATION OR MISINSTALLATION OF ITS
PRODUCTS.
The user is cautioned to observe all recommendations,
warnings, and cautions relating to the safety of personnel
and equipment as well as all general and local health and
safety laws, codes, and procedures.
The recommendations and information contained herein
are based on Allen-Bradley experience and judgement,
but should not be considered to be all-inclusive or covering every application or circumstance which may arise. If
any questions arise, contact Allen-Bradley for further
information or instructions.
1. INTRODUCTION
Trip units for Q-frame and M-frame circuit
breakers (Fig. 1-1) are available in two types:
thermal-magnetic trip functions, described in this
instruction leaflet or electronic trip functions,
covered in Instruction Leaflet 40752-072. Trip
units are listed in accordance with Underwriters'
Laboratories, Inc. Standard UL489 and satisfy the
applicable requirements of the International Electrotechnical Commission Recommendations for molded
case circuit breakers.
The trip unit includes either a fixed or an adjustable thermal element for inverse time delay on overload and an
adjustable magnetic element for protection against short
circuits. In open air at 40°C, the trip unit continuously carries a current (ln) equal to the ampere rating marked on
the trip unit nameplate without exceeding a 50°C rise at
the terminals. The National Electrical Code (USA)
requirements state that enclosed overcurrent protective
devices may be loaded to a maximum of 80 percent of
the open air rating (In).
The trip unit cover is factory sealed to prevent tampering
with the calibration. Tables 1-1 and 1-2 list catalog numbers and electrical data for trip units.
Thermal Trip: The thermal element trips the circuit
breaker within 2 hours for an overload of 135 percent and
trips in less time for higher overloads. For all currents in
excess of the magnetic setting, the tripping action is
instantaneous. In the overload trip region (up to 6 x In),
the trip current times are the same for AC or DC.
Magnetic Trip: The magnetic trip on each pole may be
adjusted by turning the adjustment button with a screwdriver (see Fig. 2-3). In the magnetic trip region (above 6
x In), the trip current levels can be up to approximately 40
percent higher for DC than for AC, depending on the rating.
Note: Trip units are calibrated at 40°C, 50/60 Hz and
DC as noted. Consult Allen-Bradley for derating at
other frequencies and ambient conditions.
Fig. 1-1 Q-Frame and M-Frame Circuit
Breaker Thermal-Magnetic Trip Unit
40752-077(2) Effective 5/02
Page 2
2. INSTALLATION
Internal Accessories: The following types of circuit
breaker internal accessories, which mount on the
trip units, are available for use. The number of
the instruction leaflet covering the installation of the
accessory is shown.
• Alarm (Signal)/Lockout (ASL) Switch..........40752-076
• Auxiliary Switch ..........................................40752-074
• Shunt Trip....................................................40752-075
• Undervoltage Release Mechanism
(Handle Reset) ...........................................40752-070
There are two major differences between Q & M-Frame
Thermal Mag trip units. The M-Frame trip units have metal
tabs that prevent them from being seated into the slots in
the side-plates of the Q-Frames as described in Sec. 2-4.
Also, the M-Frame trip unit conductors have angles on
the load end, which fit within the shapes machined in the
load conductors of the M-Frame. Conversely, the Q-Frame
trip units will not seat into an M-Frame. There are projections in the base mold of the M-Frame which interfere
with the bracket of the Q-Frame trip units and the conductors will not fit within the contours of the M-Frame load
conductor.
The installation procedure consists of inspecting and
installing the trip unit. To install the trip unit, perform the
following steps.
Note: If required, internal accessory installation
should be done before the circuit breaker is mounted
and connected. Refer to individual accessory
instruction leaflets.
2-1. Make sure that the trip unit is suitable for the
intended installation by comparing nameplate information with the existing equipment ratings and system requirements. Make sure that you are installing
the correct type of trip unit, Q or M-Frame, in the
correct type of frame. Inspect the trip unit for completeness and check for damage before installing
it in the circuit breaker frame.
Note: Trip unit center retaining screw is captive in the
trip unit mechanism pole bracket; the outer pole
screws are supplied with the breaker frame. In the
M-frame, the load-end trip unit mounting screws
are supplied with the frame.
2-2. Remove circuit breaker pan-head cover screws and
covers.
2-3. Remove trip unit outer screws and red plastic
washers from the breaker frame. Discard red plastic washers. For an M-frame, remove the
load-end trip unit mounting screws from the frame.
Note: The trip unit outer screws may be placed in the
trip unit conductor holes at this time. If preferred, a
hexagonal-head wrench may be used to position the
screws when the trip unit is in the base.
2-4. Position trip unit in base. Make sure latch bracket
pin is properly seated in slots in side plates (see
Fig. 2-1). If necessary, push circuit breaker handle
towards the closed position to help seat trip unit.
40752-077(2) Effective 5/02
Page 3
CAUTION
DO NOT EXCEED SPECIFIED TORQUE. EXCESSIVE
TORQUING WILL SHEAR SCREWS.
FAILURE TO APPLY THE REQUIRED TORQUE MAY
LEAD TO EXCESSIVE HEATING AND CAUSE
NUISANCE TRIPPING OF THE CIRCUIT BREAKER.
2-5. Screw in and tighten the trip unit retaining screws in
each pole (mechanism pole first). Torque the lineend screws to 10-12 Ib ft (13.56-16.27 N.m) (See
Fig. 2-1). For the M-frame, torque the load-end
screws to 6-8 lb ft (8.14-10.85 N.m). (See Fig. 2-2.)
2-6. Install accessory(ies), if required. For poles where
accessories are not required, install protective barriers supplied with trip unit in accessory retaining
slots.
2-7. Make sure interphase barriers are in slots in the
base of the circuit breaker.
2-8. Make sure that opening in sliding handle barrier
(captive in cover) is aligned with circuit breaker
handle.
Note: Circuit breaker cover can be installed or
removed only if the circuit breaker is in the
“TRIPPED” or “OFF” position.
ues in multiples of the trip unit ampere rating (In) as
shown in Fig. 2-3.
Note: Button must be set at detents and not at intermediate positions.
To adjust the setting, rotate each button until arrow on
button points to desired setting.
2-12. Adjust magnetic pick-up settings as required (see
Fig. 2-3).
Trip Unit Thermal Adjustment
In some trip unit types, the thermal rating (In) of the trip
unit can be adjusted by a single button (see Fig. 2-4)
within the ranges indicated in Table 1-2.
CAUTION
TO PREVENT POSSIBLE INTERNAL DAMAGE TO
THE TRIP UNIT, THE CIRCUIT BREAKER MUST BE
TRIPPED PRIOR TO CHANGING THE THERMAL
ADJUSTMENT.
2-13. Adjust thermal setting as required (see Fig. 2-4) by
rotating the thermal adjustment button until the
arrow on the button points to the desired setting.
2-9. Install the circuit breaker main cover and terminal
cover on the Q-Frame. Install the main cover and
both terminal covers on the M-Frame. Secure
with the original screws and torque them to 20-22
Ib in (2.26-2.49 N.m). (See Fig. 2-2.)
2-10. Reset circuit breaker by moving handle to the reset
position. Move handle to the ON position. Circuit
breaker should remain ON.
2-11. Press PUSH-TO-TRIP button with a small screwdriver to check manual tripping of the circuit
breaker (see Fig. 2-3).
Trip Unit Magnetic Adjustment
The magnetic element of each pole of the trip unit can be
adjusted by rotating the adjustment buttons on the front
face of the trip unit with a screwdriver. The buttons have
several settings as indicated on the nameplate with val-
40752-077(2) Effective 5/02
Fig. 2-1 Trip Unit Installed in a Q-Frame
Page 4
Fig. 2-2 Trip Unit and Covers Installation in an M-Frame
40752-077(2) Effective 5/02
Page 5
Fig. 2-3 Trip Unit Magnetic Adjustment Buttons
Table 1-1. Q-Frame Trip Unit Catalog Numbers and Electrical Data - Fixed Thermal
Catalog
No.
3-Pole
Continuous
Ampere
Rating
(l n) 40°C
140U-QTD3-D30
140U-QTD3-D35
140U-QTD3-D40
140U-QTD3-D45
140U-QTD3-D50
140U-QTD3-D60
➀
Nameplate is marked in multiples of ln.
40752-077(2) Effective 5/02
300
350
400
450
500
600
Magnetic
Trip
Range
Amperes ➀
1500-3000
1750-3500
2000-4000
2250-4500
2500-5000
3000-6000
Page 6
Table 1-2. M-Frame Trip Unit Catalog
Numbers and Electrical Data
Catalog
Number
2-Pole
MTD3-D30
MTD3-D35
MTD3-D40
MTD3-D45
MTD3-D50
MTD3-D60
MTD3-D70
MTD3-D80
Continuous
Ampere
Rating
l n @ 40°C
300
350
400
450
500
600
700
800
40752-077(2) Effective5/02
Magnetic
Trip
Range
Amperes
1500-3000
1750-3599
2000-4000
2250-4500
2500-5000
3000-6000
2800-5600
3200-6400
Page 7
NOTES
40752-077(2) Effective 5/02
Page 8
40752-077(2) Effective 5/02
Printed in U.S.A./TQC